Update libva headers to the latest release (1.2.1).

The motivation is to pick up upstream fixes and be compatible with
new VAAPI library after release 1.2.0: the function vaCreateSurfaces()
changes its prototype in API version >= 0.34, so we need to handle this
in run time.

The commands used to update third_party/libva/va are:
git clone git://anongit.freedesktop.org/libva /tmp/libva
cd /tmp/libva
git checkout libva-1.2.1
rm -rf ~/chromium/src/third_party/libva/va
find va -name \*.h -exec cp --parents \{\} ~/chromium/src/third_party/libva \;
cp ~/va_version.h ~/chromium/src/third_party/libva/va

BUG=none
TEST=on link, run through the H.264.1 conformance bitstreams, and no regression.

Review URL: https://codereview.chromium.org/62273006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@236492 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 236492